The invention relates to interworking between distributed services in a telecommunications network, especially in an intelligent network.
The rapid development of the telecommunication field has made it possible for operators to provide users with services of many different types. One such network architecture providing advanced services is called the Intelligent Network, for which the abbreviation IN is generally used. Examples of such services are the Virtual Private Network VPN, which allows the use of short numbers between subscribers of the private network, and the Personal Number, where the intelligent network re-routes calls made to the personal number in a manner controlled by the subscriber. IN-services are utilized by various networks, such as mobile communications networks and fixed networks connected to IN.
The physical architecture of the intelligent network is illustrated in FIG. 1, where the physical entities are shown as rectangles or cylinders and the functional entities located in them are shown as ovals. This architecture is described briefly below, since references will be made to an intelligent network environment in the description of the invention to follow. An interested reader may acquire a more detailed understanding of the intelligent network from ITUT recommendations Q.121X or from Bellcore""s AIN recommendations, for example. ETS 300 374-1 CoreINAP terms will be used in the description of the invention and its background, but the invention can also be used in intelligent networks implemented in accordance with other intelligent network standards.
The Subscriber Equipment SE, which may be a telephone, a mobile station, a computer, or a fax, for example, is either connected directly to a Service Switching Point SSP or to a Network Access Point NAP. A service switching point SSP provides the user with access to the network and attends to all necessary dialing functions. The SSP is also able to detect the need for an intelligent network service request. In functional terms, the SSP includes call management, routing, and service dialing functions.
The Service Control Point SCP includes Service Logic Programs SLP, which are used to produce intelligent network services. In the following, xe2x80x9cservice programxe2x80x9d will also be used as a shorter form for xe2x80x9cservice logic programsxe2x80x9d.
The Service Data Point SDP is a database containing data about the subscriber and the intelligent network which the SCP service programs use for producing individualized services. The SCP may use SDP services directly by way of a signaling or data network.
The Intelligent Peripheral IP provides special functions, such as announcements, and voice recognition.
The signaling network shown in FIG. 1 is a network according to Signalling System Number 7 (SS7), a known signaling system described in the Specifications of Signalling System No. 7 of the CCITT (nowadays ITU-T), Melbourne 1988.
The Call Control Agent Function (CCAF) ensures that the end user (subscriber) has access to the network. Access to IN-services is implemented through additions made to existing digital exchanges. This is done by using the Basic Call State Model BCSM, which describes the various stages of call handling and includes points called Detection Points DP, where the call handling can be interrupted in order to start intelligent network services. At these detection points, the service logic entities of the intelligent network are permitted to interact with the basic call and connection control capabilities. Therefore, Detection Points DP describe those points in call and connection processing where the transfer of control can occur.
In the exchange, the call set-up is divided into two parts: the call set-up in the originating half and the call set-up in the terminating half. As a rough description, call handling in the originating half is related to the services of the calling subscriber, while call handling in the terminating half is related to the services of the called subscriber. The corresponding state models are the Originating Basic Call State Model (O-BCSM) and the Terminating Basic Call State Model (T-BCSM). The BCSM is a high-level state automaton description of those Call Control Functions (CCF) needed for setting up and maintaining a connection between the users. Functionality is added to this state model with the aid of the Service Switching Function (SSF) (cf. partial overlapping of CCFs and SSFs in FIG. 1) to make it possible to decide when intelligent network services (IN-services) should be requested. When IN-services have been requested, the Service Control Function (SCF), including the service logic of the intelligent network, attends to the service-related processing (of call handling). Thus, the Service Switching Function SSF connects the Call Control Function CCF to the Service Control Function SCF and allows the Service Control Function SCF to control the Call Control Function CCF.
FIGS. 2a and 2b show simplified flow charts of the Basic Call State Model O-BCSM (FIG. 2a) and T-BCSM (FIG. 2b), which include both Points in Call (PICs) identifying CCF activities associated with call handling and Detection Points (DPs). Transitions in the BCSM are indicated with arrows. The Points in Call and Detection Points in FIGS. 2a and 2b are not described here in any closer detail but merely in relation with the invention later on.
The intelligent network service is implemented in such a way that in connection with the encounter of service-related detection points, such as DP1-10 and DP12-18 in FIGS. 2a and 2b, proceedings in the call handling model BCSM are suspended, and the Service Switching Point SSP asks the Service Control Point SCP for instructions with the aid of messages relayed over the SSP/SCP interface. In intelligent network terminology these messages are called operations. The SCF may request, for example, that the SSF/CCF perform certain call or connection functions, such as charging or routing actions. The SCF may also send requests to the Service Data Function (SDF), which provides access to service-related data and network data of the intelligent network. Thus the SCF may request, for example, that the SDF fetches data concerning a certain service or that it updates this data.
The Intelligent Network functions involved in interaction with the subscriber are supplemented by a Specialised Resources Function SRF providing an interface for those network mechanisms. Examples of such functions are messages to the subscriber and the collection of the subscriber""s dialing.
The following is a brief description of the role of the functional entities shown in FIG. 1 in terms of IN-services. The CCAF receives the service request of the calling party, typically made by the calling party lifting the receiver and/or dialing a certain number series. The CCAF relays the service request further to the CCF/SSF for processing. The CCF has no service data, but it is programmed to identify those detection points where a SCP visit might be made. The CCF interrupts the call set-up for a moment and gives the service switching function SSF data about the detection point encountered (about the stage of the call set-up). It is the duty of the SSF through use of predetermined criteria to interpret whether a service request to the intelligent network is necessary. If this is the case, the SSF sends to the SCF a standardized IN-service request, including data related to the call. The SCF receives the request and decodes it. Then it works together with the SSF/CCF, SRF, and SDF in order to produce the requested service for the end user.
As was presented above, service is started when the SSF sends to the SCF a standard IN-service request. The service request may be sent during certain stages of the call. FIG. 3 illustrates a few basic operations of a state-of-the-art function of an intelligent network at detection points. At Point 21 the SSP sends to the SCP an InitialDP service request, including basic data on the call for starting the intelligent network service. Thereupon the arming of detection points in the SSP follows. At Point 22 the SCP sends to the SSP a RequestReportBCSMEvent operation telling the SSP which detection points it should report to the SCP. Next, at Point 23 the SCP typically sends charging and/or interaction operations, such as ApplyCharging (e.g. a request for a charging report) or PlayAnnouncement (give an announcement to the subscriber). At Point 24 the SCP sends to the SSP a routing instruction, such as Connect (route the call to a new number) or Continue (continue the call set-up). When the SSP meets the detection point reserved by the SCP, the SSP sends to the SCP an EventReportBCSM operation at Point 26.
Detection points determined in the call model of an intelligent network are the primary mechanism for reporting various events occurring during the call establishment. The operations 21-24 in FIG. 3 described above relate to a detection point called the Trigger Detection Point (TDP). The SSP may make an initial inquiry concerning a service to the SCP only at a TDP service-related detection point. Therefore, a new IN-service is initiated at the TDP. At what is termed a Trigger Detection Point-Request (TDP-R), the processing of the call is stopped until the SSP receives instructions from the SCP. Thus, a control relationship is formed between the SSP and the service program in question. At the Trigger Detection Point-Notification (TDP-N), only notification of the encounter of the service-related detection point is sent from the SSP to the SCP, and call handling is continued without waiting for instructions from the SCP. Another type of detection point is the Event Detection Point (EDP). Point 26 in FIG. 2 shows a moment when in the course of a call an EDP detection point is encountered. The SSP reports on the encounter with this service-related detection point to the SCP, which at Point 28 sends additional call instructions to the SSP. The Event Detection Point-Request (EDP-R) is a detection point where the processing of the call is suspended until the SCP sends additional instructions. The arming of the EDP-R detection points creates a control relationship between the SSP and a particular service program of the SCP. A control relationship is established when a session is going on between the call set-up half and the SCF, during which the SCF may give instructions that change the handling of the call. In a monitor relationship the SCP is not able to affect the progress of the call handling; it can only ask the SSP to report on various events relating to the call. In a monitor relationship, only the Event Detection Point-Notification (EDP-N) may be armed.
In accordance with the current intelligent network standard, several monitor relationships but only one control relationship can relate to a call (single point of control). However, it has been proposed that a multiple point of control (MPC) be established wherein several service programs can interact with the call handling. The problem with such a multiple point of control is that individual service programs are not aware of the call handling instructions the SSP has received from other service programs simultaneously controlling the call. Therefore, the call can be released by one service program sending a ReleaseCall operation, and the other service programs notice that the call has ended with an error, for example. This prevents controlled release of all services related to the call. In multiple point of control, it is known that service programs within one SCP can communicate with one another. The problem in facilitating the communication within one SCP is that the service programs need to know addresses of one another, and they usually need to conform to the same protocol, such as CoreINAP or CAMEL (Customized Applications for Mobile Enhanced Logic).
It is the purpose of this invention to implement effective interworking between distributed services in a telecommunications network, especially in an intelligent network.
This purpose is achieved through a method and a telecommunications network according to the invention which are characterized by the independent claims. Different embodiments of the invention are presented in the dependent claims.
The invention is based on the idea that at least one new Interworking Point is introduced to the call handling model, and with the aid of this Interworking Point the interworking between the distributed services is implemented. The Interworking Point can be defined as either a point where instructions received from one service program are reported to interested service programs or as where a service to be carried out by the responsible service program is requested by some other service program. The interworking points are armed by the service programs, which are in turn informed of the encounter with an interworking point.
Interworking of distributed services has the advantage that service programs can request service within the authorization of other service programs without knowing the service program performing the requested service. The interworking of distributed services is thus made effective and facile. The service programs need not all have the same protocol, nor do they need to know the addresses of the other service programs with which they are interworking.
Another advantage of the invention is that it eliminates the need for a complicated mechanism for communication between service programs or service control points, as the control of interworking is maintained at the switching point.